Re : chebyechev coversion of resistance value of Cernox resistor into temperature

[Manivannan]

Sir,

  I am in a trouble in coverting the data collected through Lab Veiw (6) VI.

  I am using Cernox (1030 - Lakeshore, USA) temperature sensor for monitoring the temperature in my experiment. Using the variation in the cernox resistance to the temperature, i can able to find the exact temperature.

  The convertion of the reistsnce to temperature will be calculated by a chebychev polynomial fit of the cernox resistance.

   Right now i am doing this in a c programme. I want to do it in the LabVeiw itself.

   Since i am new to the Labview i am struck up with this task. I am in an urgent to clear this task.

   Pl. help me in giving me a VI that can convert the resistance into Temperatrue.

   I am herewith  attaching the data for conversion  as apdf file .

[Vincent_Carpentier]

Hi Manivannan,

Actually there is a Chebyshev Polynomial VI in LabVIEW 8.20 that I saw.  Unfortunately, it is not in the Base Package.  Therefore, you need to have the Full or Professional version of LabVIEW.

I looked at LabVIEW 6.0 and there is the Chebyshev Approximation VI that I think would do the job for you.  It is located at Functions->Mathematics->Optimization

Look at the Help file and that should tell you how to use it.

Thanks,

[julienAu]

Hello,

I'm working with the same type of sensors (lakeshore Cernox). I want to calibrate a sensor by myself. To do this, I want to measure the resistance of an uncalibrated sensor, and in a same time the temperature from a calibrated sensor. So I will have an 2D array, consisting of Temperatures and Resistances. Then, I want to calculate Chebychev coefficients (like A0, A1...), similar to the .pdf you joined.
But I didn't find any function to calculate Chebychev coefficients from experimental values. So,

Do you know how determine Chebychev coefficients from experimental values ?

[Jeffrey_Zola]

Hi, Julien- You are responding to a thread that is several years old!

Although I am not familiar with the temperature sensors you are using or the model to calculate temperature from the resistance, I do have a couple suggestions for you to convert resistance to temperature.

First, There are shipping examples for RTD and thermistor resistance to temperature conversion that use a parabolic model. Each has a pull-down of standard device types (and the VI uses a lookup of the polynomial coefficients) and also has a "custom" option, which allows you to enter the three coefficients for a parabolic model.

Second, as it appears that your calibration report provides you with fifth-order coefficients, you can use a formula node to convert a resistance to a temperature based on whatever calculation you would like. You can even work it out to use 2D arrays or arrays of clusters or similar to store the specific coefficients that a calibration service provides you for each sensor you use.

It sounds like you want to use one supplier-calibrated sensor to be a standard for you to calibrate additional units. Assuming you have sufficient data for each device along an appropriate temperature range, you can calculate the model coefficients mathematically. I suggest you familiarize yourself with your sensors and with the examples that ship with LabVIEW. A good place to start studying these temperature devices is:  http://www.lakeshore.com/Documents/F010-00-00.pdf.

If you need help with components of a LabVIEW program for your conversion, data collection, or coefficient derivation, you should post specific questions in a new thread and show the forum what you have done and where you need help.

Jeff Zola